benefit of the Fast Restore feature

Q

What is the benefit of the Fast Restore feature?

A

The AD8232 implements an AC-coupled solution. This means it removes the dc and near-dc frequencies via a high pass filter. The time required to remove dc offsets can be very long if the cut-off frequency is low (1Hz or less). This settling time can be impractical. For example, it can delay the measurement for several seconds after making contact with the subject. This situation repeats every time contact is lost or the electrodes move slightly due to motion artifacts.

If Fast Restore is enabled (via a digital input), the Fast Restore circuit automatically detects when the signal is lost and momentarily increases the corner frequency of the high pass, thus making the settling time much shorter. This is achieved by switching in a small resistor in parallel with the high value external resistor.

It is important to note the part automatically switches back to normal once the signal is settled and that this feature performs automatically without the intervention of the processor.